Rubbery polymers of moderately low Mooney viscosities are desired in many sponge applications, such as rug underlay manufacture, since the lower viscosity polymers afford a sponge rubber of sufficient drape for such applications.
Unfortunately, polymers of moderately low Mooney viscosity are not convenient dry crumbs, but rather exhibit the characteristic of an undesirably sticky rubber crumb, making drying and handling very difficult. However, these relatively low Mooney viscosity type products are exactly what is desired so as to be able to provide a sponge that ultimately will adequately drape during rug underlay manufacture. Thus, dichotomy has existed, since the rubber manufacturer prefers to make a high enough Mooney viscosity rubber such that handling and drying of the rubber crumb product is relatively easy and economical. But, the higher Mooney viscosity rubbers are just not adequately suitable for many sponge rubber applications, as mentioned.